Short answer: a good player can profit anywhere.
Long answer: it depends on what you want.
Deposit bonus is good, but can be easily found, to the point where it can be overwhelming to choose.
For a small bankroll, titan has a nice deposit up to $300 for 200% in bonus money, and if you earn the full amount steadily, you'll also have nearly enough to exchange earned points for the $1750 package. (Or is there a reduction?)
For a larger bankroll, go for the FT or P* bonus, up to $600 gets 100% bonus, plus a decent rakeback on top of that. (FT is a fixed 27%, P* is variable.)
If you hate HUDs and tracking software, go for cake poker, they banned every hud, and on top of that, you can change your nick every week, if you're skitzo like that. 
Everest and betfair are also great to bonus whore on, with a fixed bonus regardless of deposit. The downside there is they're smaller, and so you'll have less tables on the limit you enjoy.
Do not be afraid to try new rooms, and it's perfectly acceptable to try out a new site for a bonus period, then return to an old favorite, or join a site solely for the freerolls.
